1. Field of the Invention
The present invention relates to damping devices such as those including fluid filled elastomeric members and the like and more specifically to an improved arrangement which permits the damping characteristics to be controlled by sensing the parameters which vary with the vibration and producing a suitable control signal which can be applied to the member.
2. Description of the Prior Art
JP-A-60-104828 discloses an arrangement wherein an damper is comprised of an annular rigid member on which a main elastomeric body and a flexible elastomeric diaphram are supported in a manner an enclosed space which is filled with a suitable working fluid which exhibits rheopectic properties. A partition member is disposed within the space to define first and second chambers. The partition is arranged to define an elongated rectangular cross-sectional communiction passage therein. The partition includes electrodes which are disposed in the communication passage in a juxtaposed manner. These electrodes are connected with a control circuit which selectively applies a voltage thereacross.
FIG. 1 is a model which depicts the arrangement of a device disclosed in JP-A-60-104828 as a system having a single degree of freedom. In this model Fk denotes the applied vibration induced spring force which causes displacement while Fc denotes the damping force produced. Ftotal denotes the vibrational force which is transmitted through the device. As shown in FIG. 2, when Fk and Fc are in phase, the damping force is attenuated, and when the two are out of phase or in what shall be referred to as a reversed phase condition, the damping force is amplified.
In this arrangement the fluid which is sealed in the elastomeric arrangement is arranged to flow through the orifice in a manner wherein the fluid within the orifice passage arrangement acts a mass, and the accompanying fluid flow induces an expansion of the elastomeric body in a manner to define a spring effect. While the vibration frequency remains just below that at which resonance occurs the dynamic spring constant of the arrangement is effectively lowered and a dynamic damping effect is produced.
However, in actual fact this device cannot be represented by a system having only a single degree of freedom in that the compressive spring component and the expansive spring component tend to develop a phase difference which varies between 0 and 18 degrees and as a result adequate attenuation of vibration transmission cannot be achieved under a wide range of operating conditions.